function OpenAdViewability(config) {

    this.check = {
        percentViewable: 0,
        percentFps: 0,
        percentIntersection: 0,
        acceptedViewablePercentage: 50,
        acceptedMrcPercentage: 50,
        viewabilityStatus: false,
        duration: 0,
        measureTime: 3000
    };

    const configNew = config || {};
    Object.assign(this.check, configNew);

    this.timer = null;
    this.statusCallback = null;
    this.startTime = null;
    this.viewable = 100;
    this.vcStarted = false;

    this.config = {};

    this.log = function () {
        if (this.config.debug || this.config.showLog) {
            var conArg = ["%cMOVIEADS-BN OAV: ", "background-color: orange; color: black; font-weight: bold"];
            var mainArguments = Array.prototype.slice.call(arguments);
            conArg = conArg.concat(mainArguments);
            console.log.apply(console, conArg);
        }
    };

    this.DEBUG_MODE = false;

    this.cancelCheck = function () {
        window.cancelAnimationFrame(this.timer);
    };

    this.getTime = function () {
        return 'object' === typeof window.performance ? window.performance.now() : new Date().getTime();
    };

    this.initViewabilityCheck = function () {
        if (this.vcStarted) {
            return;
        }

        this.vcStarted = true;

        var io  = new IntersectionObserver(function (entries) {
                for (var eKey in entries) {
                    var entry = entries[eKey];
                    this.viewable = Math.floor(entry.intersectionRatio*100);

                    if ('isIntersecting ' in entry) {
                        console.log('isIntersecting', entry.isIntersecting);
                    }
                    if ('isVisible ' in entry) {
                        console.log('isVisible', entry.isVisible);
                    }

                    console.log('viewable', this.viewable);
                }
            }.bind(this),
            {
                threshold: [0,0.1,0.15,0.20,0.25,0.30,0.35,0.40,0.45,0.50,0.55,0.60,0.65,0.70,0.75,0.80,0.85,0.90,0.95,1],
                trackVisibility: true,
                delay: 100
            });
        io.observe(document.body);

        window.addEventListener('beforeunload', () => {
            if (typeof IntersectionObserver != 'undefined') {
                io.unobserve(document.body);
                io = null;
            }
        });
    };


    this.checkViewability = function (statusCallback) {
        this.initViewabilityCheck();
        this.statusCallback = statusCallback;

        this.startTime = this.getTime();
        this.timer = window.requestAnimationFrame(this.countDownStart.bind(this));
    };

    this.countDownStart = function() {
        this.log('MRC countDownStart');
        let viewable = this.checkViewable();

        if (!viewable) {
            this.log('OAV MRC TRACKER STATS, visibility: ',this.check.percentFps, ', mrc vis: ',this.check.percentFps, 'accepted fps: ', this.check.acceptedMrcPercentage, ' viwability: ', this.check.acceptedViewablePercentage, 'vw: ', this.viewable, 'state:', document.visibilityState);
            this.startTime = this.getTime();
            this.resetCheck();
        }
        var offset = this.getTime() - this.startTime;

        var timeUp = offset >= this.check.measureTime;
        this.check.duration = offset;

        if (timeUp) {
            this.check.viewabilityStatus = (this.check.percentViewable >= this.check.acceptedViewablePercentage);

            // if (!this.DEBUG_MODE) {
            //     window.cancelAnimationFrame(this.timer);
            // }

            if (this.check.viewabilityStatus) {
                this.statusCallback(this.check);
            }
        } else {
            this.timer = window.requestAnimationFrame(this.countDownStart.bind(this));
        }
    };

    this.resetCheck = function () {
        this.check.percentFps = 0;
        this.check.percentIntersection = 0;
        this.check.percentViewable = 0;
        this.check.duration = 0;
        this.check.viewabilityStatus = false;
    };

    this.checkViewable = function () {
        let visibility = this.viewable;
        //let mrc = Math.floor(this.ad.fps*100/this.ad.baseFps);
        // mrc = mrc > 100 ? 100 : mrc;
        //
        // this.check.percentFps = mrc;
        this.check.percentIntersection = visibility;

        if (document.visibilityState != 'visible') {
            this.startTime = this.getTime();
            return false;
        }

        // this.check.percentViewable = Math.floor((visibility+mrc)/2);
        this.check.percentViewable = Math.floor(visibility);

        // if (visibility < this.check.acceptedViewablePercentage || mrc < this.check.acceptedMrcPercentage) {
        if (visibility < this.check.acceptedViewablePercentage || visibility < this.check.acceptedMrcPercentage) {
            return false;
        }


        return this.check.percentViewable;
    };
}